Been playing around with some black glass (or film) recently. Here are a few of my first attempts. I can get up to 20 minute exposures in broad daylight if I push everything to its max (or should I say min), but these are all around 4-5 minutes each. All shot with the 5D mkiii and the 14mm 2.8 L II.

Interesting... I have to wonder how bad hot pixels might be with such exposures.

If anyone needs a high density ND, you could try Baader astrosolar film. It comes in two versions, the stronger version is >16 stops effective (they say >99.999% reduction) and is made specifically to make direct viewing of the sun safe.

Interesting... I have to wonder how bad hot pixels might be with such exposures.

If anyone needs a high density ND, you could try Baader astrosolar film. It comes in two versions, the stronger version is >16 stops effective (they say >99.999% reduction) and is made specifically to make direct viewing of the sun safe.

I was just thinking of that. I've got a Baader filter for the 400. Finding something to shoot with an ultra-long exposure with a 400 might be a bit of a challenge, though....

Hey guys, sorry I've been busy at work all day and the "notify me of replies" feature only seems to work sometimes (and in this case, not at all). So, by black glass I was referring to a very dark ND filter, in this case its not technically glass, but rather a gel. I'm using a 4.0 and I think that equates to 14 stops, and then I'm using f16-22 and iso 50-400, depending on the scene. Like I said at 50iso and f22, I think I could push a 20min exp no problem (and maybe even 40min, as that would only be 1 stop brighter than 20min). As for f22 degrading IQ, I wouldn't worry about it, your not going to get great IQ, no matter what you do, on a 5+ minute exposure (camera shake, movement, changing light, light refraction, wind ect), its more about the effect than the IQ. As for hot pixels, you definitely get quite a few, and I suppose I could use a subtraction image, but I'm too impatient, so I just deal with them in post. No HDR in these, as I obviously didn't need it, one thing I've found is that the DR in these super long exposures is incredible, I haven't figured out why from a physics stand point (to be honest I haven't even looked into it yet), but I'm sure there is a reason. I have plans to shoot a few locations with long exposures like these that would have enough DR to necessitate HDR, which I'd be more than happy to post. I'd love to see some of the stuff you guys have come up with using similar techniques...